Climate Response to Pulse Versus Sustained Stratospheric Aerosol Forcing

Abstract

Solar geoengineering has been suggested as a potential means to counteract anthropogenic warming. Major volcanic eruptions have been used as natural analogues to large‐scale deployments of stratospheric aerosol geoengineering, yet difference in climate responses to these forcings remains unclear. Using the National Center for Atmospheric Research Community Earth System Model, we compare climate responses to two highly idealized stratospheric aerosol forcings that have different durations: a short‐term pulse representative of volcanic eruptions and a long‐term sustained forcing representative of geoengineering. For the same amount of global mean cooling, decreases in land temperature, precipitation, and runoff in the pulse case are much larger than that in the sustained case. The spatial pattern changes differ substantially between these two cases. Thus, direct extrapolations from volcanic eruption observations provide limited insight into impacts of potential stratospheric aerosol geoengineering. However, simulations of volcanic eruptions can be useful to test process representations in models that are used to simulate geoengineering deployments.

Robust winter warming over Eurasia under stratospheric sulfate geoengineering – the role of stratospheric dynamics

“…For example, the widely observed eruption of Mount Pinatubo in June 1991 injected around 18 Tg SO 2 into the stratosphere (Guo et al, 2004) and reduced global and annual average surface temperatures by 0.5 • C for 2 years following the eruption (Soden et al, 2002), while other large, explosive eruptions of the past century reduced global average temperatures by 0.1-0.2 • C (Robock and Mao, 1994). A key limitation of the analogy to geoengineering is the transient nature of volcanic perturbations compared to the hypothetically continuous deployment of sulfate geoengineering (Duan et al, 2019;Robock et al, 2008Robock et al, , 2013. Differences between the impacts of volcanic eruptions and sulfate geoengineering could also arise from the choice of material injected in the latter (sulfur dioxide, SO 2 , versus sulfate directly) and the choice of injection locations, both of which could result in different aerosol distributions.…”

Searching for the Logic of Ignoring Earth’s Global Physical Conditions

“…For example, a volcano sends vast quantities of particles into the atmosphere which block the sunlight and cool the planet. Replicating the volcano conditions by sending vast quantities of sulfates into the atmosphere would be a geoengineering solution to counter climate change and thus reverse the global warming [123]. In principle this is no different than modifying earth with construction of a road to get from point A to point B.…”

Uncertainty and the basis for confidence in solar geoengineering research

“…Since geoengineering has never been deployed, bounds on potential uncertainties are reliant on information from natural analogues, such as large volcanic eruptions. These analogues, however, often provide limited information 72 ; differences in aerosol microphysics 73 and climate responses 74 , for example, will vary markedly when comparing pulse volcanic eruptions and sustained injections through SAG. In addition, there is sometimes no natural analogue that can be used.…”